The research team, led by Damian Cruse and Adrian M. Owen of the
University of Western Ontario, gave simple instructions to 16 people
said to be “vegetative”: each time you hear a beep, imagine squeezing
your right hand into a fist. The subjects were given this task and
another — hear a beep, wiggle your toes — and ran through up to 200
repetitions.
In healthy people who executed these instructions, the EEG picked up a
clear pattern in the premotor cortex, the area of the brain that plans
and prepares movements; the electrical flare associated with the hand
was distinct from that associated with the toes.
The brains of three of the supposedly vegetative people showed precisely
that; the subjects were a 29-year-old, a 35-year-old and a 45-year-old,
all men who had been pronounced vegetative three months to two years
previously.
“That’s about 20 percent of the patient group, producing responses that were identical to healthy volunteers,” said Dr. Owen.

We are assured this has nothing to do with Terri Schiavo.

The case of Terri Schiavo, a Florida woman who became unresponsive after
her heart stopped and who was removed from life support in 2005, became
a political and family controversy. Doctors say it is unlikely that the
EEG test would have changed the diagnosis in that case.

This conclusion is necessarily based on nothing whatsoever. We can't tell what's happening in the brain without this test, and she never got this test so.... Whatever. Don't we all feel reassured?